In the US biennial screening mammography is recommended for average-risk women aged 50–74 because the benefits outweigh the harms. For women with increased risk starting screening at age 40 may have a similar harm-benefit ratio.
Determine the threshold relative risk (RR) at which the harm-benefit ratio of screening women aged 40–49 equals that of biennial screening for women aged 50–74.
Comparative modeling study.
Surveillance, Epidemiology, and End Results, Breast Cancer Surveillance Consortium, medical literature.
A contemporary cohort of women eligible for routine screening.
Mammography screening starting at age 40 vs. 50 with different screening modalities (film, digital) and screening intervals (annual, biennial).
Benefits: life-years gained, breast cancer deaths averted; harms: false-positive mammography examinations; and harm-benefit ratios: false positives/life-year gained, false positives/death averted.
Results of Base-Case Analysis
Screening average-risk women aged 50–74 biennially yields the same false positives/life-year gained as biennial screening with digital mammography starting at age 40 for women with a 2-fold increased risk above average (median threshold RR 1.9; range across models 1.5–4.4). The threshold RRs are higher for annual screening with digital mammography(median 4.3; range 3.3–10) and higher when false positives/death averted is used as outcome measure instead of false positives/life-year gained. The harm-benefit ratio for film mammography is more favorable than for digital, because film has a lower false-positive rate.
Results of Sensitivity Analysis
The threshold RRs changed slightly when a more comprehensive measure of harm was used and were relatively insensitive to lower adherence assumptions.
Risk was assumed to influence onset of disease without influencing screening performance.
Women aged 40–49 with a 2-fold increased risk have similar harm-benefit ratios for biennial screening mammography as average-risk women aged 50–74. Threshold RRs required for favorable harm-benefit ratios vary by screening modality, interval, and outcome measure.
Primary Funding Source
National Cancer Institute.